1. Field of the Invention
The present invention relates to delaying the ignition of, and extinguishment following ignition of, an oil or gas fire on a oil drilling rig in a blow-out. More particularly, the present invention relates to a spool apparatus which is inserted in the "stack" around a section of drill pipe directly above and adjacent to the "Hydril" and fed by a plurality of conduits extending between the spool apparatus and a source of pressurized chemicals, which pressurized chemicals are injected through valve openings in the spool apparatus directly into the flow of hydrocarbons around the drill pipe upon activation of the system.
2. General Description and Prior Art
There is an ever-present danger of the occurence of a blowout and resulting fire on oil drilling rigs. The present invention provides equipment for delaying the ignition of such a fire in order to enable the workers to evacuate, or for extinguishing the fire in the event ignition does occur. It is a well recognized fact that the occurence of a blowout involves immediate danger to the lives and safety of workers on the oil platform, an enormous expense involved in controlling the blowout and extinguishing the resulting fire, the loss and waste of valuable fuel, and the detrimental effects to the surrounding environment.
At present, oil drilling rigs are equipped with one or more devices located around the drill pipe and above the casing for preventing blowouts called a blowout preventer (BOP). The blowout preventer, usually by a ramming action, is designed to smash, pinch and scissor the drill pipe shut hopefully closing off the flow of hydrocarbons in a blowout. Also, located above the BOP is situated the "Hydril" which apparatus is utilized for sealing around the drill pipe to prevent further loss of hydrocarbons after occurence of a blowout. However, should these two systems fail, and such has occured in the past, the catastrophic results iterated above ensue. Thus, there is a great need for an additional system which could at least delay the ignition, if not extinguish the fire, following a blowout in order to allow, for example, evacuation of the workers.
The BOP'S (usually numbering one to three) and the "Hydril" form a section of elements above the well casing called the "stack", as these elements are stacked one on top of the other around the drill pipe and connected to either by bolt-flange connections above the well casing and below the mud return line. All of this part of the well system is located below the oil rig floor and its associated equipment.
For example, the Wiseman U.S. Pat. No. 3,620,299, issued Nov. 16, 1971, teaches the use of refrigerated CO.sub.2 as a chemical to inject through a plurality of apertures in three set of extinguishment manifolds which surround the drill head, the CO.sub.2 being injected adjacent to the drill head. Additionally Wiseman injects CO.sub.2 through the drilling mud kill line into the casing below the blowout preventers. The Wiseman system, however, requires that an enourmous quantity of pure CO.sub.2 gas be stored at 0.degree. F. at 300 p.s.i. Also, the CO.sub.2 is strayed on the exterior of the drill head once the blowout has occured and the hydrocarbons have been released into the atmosphere, or into the casing below the BOP'S which is a very high pressure area in a blowout, subject to great back pressure, and would not be effective and would cause severe problems including partial or complete isolation of the CO.sub.2 from the hydrocarbons if the "Hydril" at least partially works. Wiseman U.S. Pat. No. 3,792,474, issued Jan. 1, 1974, regarding a method for extinguishing oil well fires, also teaches the use of refrigeraged CO.sub.2 being injected outside of the drill head or into the casing below the BOP'S.
In both Wiseman patents, the CO.sub.2 gas is used in pure form, refrigerated, and injected on the exterior of the drill head or into the flow of hydrocarbons within the casing. Also, the Wiseman patents require the utilization of elaborate electrical triggering mechanisms and securing mechanisms for the activation of the system.
The present invention can utilize highly pressurized CO.sub.2 gas; however, in the invention this pressurized gas functions primarily as a press for chemical mono-potassium phosphate, and many other gaseous presses are available. Unlike the Wiseman process, the invention does not require refrigeration of the CO.sub.2 in order to be put into use, since the present invention does not rely solely on CO.sub.2 gas for accomplishing its objective. Also, unlike Wiseman, and other prior art references, the system of the present invention does not have its chemical injected outside of the drill head or into the casing below the BOP(s), but, rather, the spool apparatus of the invention, being located in the "stack", enables the admixture to be injected into the flow of hydrocarbons while the flow is still contained in the drill pipe stem, regardless of whether or not the "Hydril" and/or the BOP(s) work, since the areas of injection are in the "stack" above the BOP(s) and "Hydril" and above the casing rather than through it. This is an important feature.
Since the point of ignition of the flow of hydrocarbons can only occur after oxygen has been introduced occur after oxygen has been introduced into the flow, the injection of the CO.sub.2 mono-potassium phosphate admixture enables the hydrocarbons to become saturated with the admixture, prior to exposure to the oxygen source in the surrounding atmosphere at the point of the blowout. This early introduction of the admixture while still in the casing will function to delay the ignition, if ignition occurs at all, and to possibly extinguish the fire following a blowout in the event the system is not activated prior to the fire commencing following the blowout.
An additional feature of the present invention is the manual activation of the system. It does not require the use of electrical systems for sensing or triggering the activation of the system, as does the Wiseman process. In fact, in the invention, the manual triggering mechanism may be located at various locations on the rig.
The following table lists a number of prior art devices and methods which have been patented and which involve the prevention of or ignition of oil well rig fires, and other related devices involved in the process.
______________________________________ PRIOR ART PATENTS ______________________________________ 2,295,571 H. Ensminger, et al September 15, 1942 2,840,166 J.E. Eckel, et al June 24, 1958 3,620,299 B.W. Wiseman, Jr. November 16, 1971 3,692,117 A.G. Wright September 19, 1972 3,792,458 J. Slack January 1, 1974 3,782,474 B.W. Wiseman, Jr. January 1, 1974 3,905,424 A.A. Elwood September 16, 1975 ______________________________________
The several prior art devices involved in the delaying of ignition or extinguishment of off-shore rig fires utilize in all cases the chemicals, principally CO.sub.2, in a supercooled state, so that enough of the pure gas stored is available for success of the system. The result is that a costly and cumbersome refrigeration process is required. The liquified CO.sub.2 must also be maintained under high pressure in its liquid state. The present invention is contrast would require no refrigeration of the chemicals whatsoever, and, although the CO.sub.2 must be stored under pressure, such pressurization on oil rigs is easily accomplished. Additionally and more importantly the chemicals are injected directly around the drill string and directly into the hydrocarbon flow before exposure to the ambient, and above the BOP(s) and the "Hydril". Also the chemicals are mixed through the curious check valving sub-systems used in the present invention.
3. General Discussion of the Present Invention
The present invention provides for an apparatus and a method primarily for delaying the ignition of, and for possibly extinguishing, the combustion of an oil rig fire following a blowout. The invention is comprised of a spool apparatus which is incorporated in the "stack" located directly above and adjacent to the "Hydril" and below the mud return line element fixedly attached to each by a steel ring flange seal with bolts. The spool apparatus is so aligned that the spool's interior cylindrical vertical opening serves as part of the passageway for the return mud around the drill pipe.
A series of chicksaw conduits or lines connect to the spool at equal distances apart so that an independent line connects preferably in each quadrant of the spool's exterior circumference through a check valve. The conduit lines serve to transport the chemicals from the chemical course, or storage tanks, to the spool for injection into the interior of the spool into the flow of hydrocarbons should a blowout occur. The conduit lines would be equipped with a swivel manifold approximately, for example, every six feet, so as to achieve simple flexing between the storage tanks and the spool apparatus.
The source of the chemicals can be for example a series of three storage tanks supported upon a skid unit located in a convenient location on or near the rig platform. The skid units could contain for example one-3,000 pound high pressure cylinder, containing a chemical, for example mono-potassium phosphate, and two 500 pound cylinders containing pressurized carbon dioxide. The 3,000 pound cylinder would have extending out from it a control head through which the chemical mixture would flow to the spool apparatus. The control head valve could be for example activated through a spring-loaded head on the firing mechanism which could be manually operated.
In the event a blowout should occur during that crucial time between when the flow of the hydrocarbons are not prevented during delay or failure of the "Hydril" and/or blowout preventer(s), the present invention could be activated manually from various stations on the rig floor, triggering the spring loaded firing mechanisms. The activation would allow the CO.sub.2 and K-PO4 to flow out of the tanks through the control head into the chicksaw lines further mixing again in the spool apparatus for injection through the four check valves into the flow of hydrocarbons around the drill pipe. The firing of the invention would cool the admixture of CO.sub.2, K-PO4 and hydrocarbons at the drill head to 190.degree. below 0.degree. F., and mix with the flow of hydrocarbons flowing through the drill pipe, thus establishing a mixture of chemical and hydrocarbons which would be much less likely to ignite upon exposure to the atmosphere.